HU, HUWA هو.
The personal pronoun of the third person, singular, masculine, HE, i.e. God, or He is. It occurs in the Qur’an in this sense, e.g. Surah iii, 1 لا اله الا الاةAllahu la ilaha illa Huwa, “God there is no god but HE,” which sentence is called the nafy wa isbat (or that which is rejected), “there is no god,” and that which is affirmed, “but He.” The word is often used by Sufi mystics in this form: لا يعلم ما هو الا هو يا هو يا منya hu, ya hu, ya man la ya’lamu ma hu illa hu, “O He (who is), O He (who is), O He whom no one knows what He Himself is but Himself.” Some commentators have supposed the word Hu to stand for the exalted name of God, the Ismu ‘l-a’zam, which Muslim doctors say is only known to God. [JEHOVAH, ISMU ‘L-A’ZAM.]
Based on Hughes, Dictionary of Islam